The invention relates to an epidural cannula for local anesthesia.
In epidural anesthesia, the point and the opening must be between the ligamenta flava and the dura mater. With conventional needles of constant diameter (see for example U.S. Pat. No. 2,922,420), the necessary force for injection is abruptly reduced at the moment the cannula point has penetrated the ligamenta flava, so that the risk of an unintended perforation of the dura mater increases. To prevent this, the physician using the epidural cannula must be skilled and experienced.
A cannula for use in operations is known from U.S. Pat. No. 3,081,770, of which the cannula body has a cross-sectional change at a distance from the cannula point. The area between the cross-sectional change and the cannula point having a central opening is rectangular or oval in cross-section.
The problem underlying the present invention is to provide an epidural cannula of the type mentioned at the outset such that it is largely ensured that an unintended perforation of the dura mater is prevented, i.e. it is ensured that the cannula point is inside the epidural area with its opening at a distance from this membrane for anesthesia or puncture.